1. Field of the Invention
Compositions of matter that have high electrical capacitance, and articles comprised of such compositions which may be used as ultracapacitors in electrical circuits.
2. Description of Related Art
In recent years, there have been significant advances in the preparation of new compositions of matter (and uses thereof and/or products made therefrom), such materials including microscopic tubular particles, also known in the art as tubules, microtubules, nanotubules, microtubes, and nanotubes. In certain contexts, such particles may also be referred to as rods or needles. One example of such tubular particles is the carbon nanotube, which, in various forms, may have a diameter of between about one nanometer and several hundred nanometers, and a length of up to several thousand nanometers long.
These nanotubes, and many other microtubular materials do not occur in nature, or at least not in substantial quantities that make such microtubular materials useful in formulating compositions of matter and/or products in high volume at low cost. Such microtubular materials typically must be synthesized, usually in gram-sized or smaller quantities, resulting in unit manufacturing costs for compositions or products including such microtubular materials that are exceedingly high.
In contrast, there is one type of inorganic microtubular material that does occur in nature in large quantities in mineral form. Such material belong to the kaolinite group of clay minerals, and is described in U.S. Pat. No. 5,651,976, “Controlled release of active agents using inorganic tubules,” of Price et al., the disclosure of which is incorporated herein by reference. In this patent, Price et al. describe the kaolinite group of minerals as follows:
“Several naturally occurring minerals will, under appropriate hydration conditions, form tubules and other microstructures suitable for use in the present invention. The most common of these is halloysite, an inorganic aluminosilicate belonging to the kaolinite group of clay minerals. See generally, Bates et al., ‘Morphology and structure of endellite and halloysite”, American Minerologists 35 463-85 (1950), which remains the definitive paper on halloysite. The mineral has the chemical formula Al2O3.2SiO2.nH2O. In hydrated form the mineral forms good tubules. In dehydrated form the mineral forms broken, collapsed, split, or partially unrolled tubules.
“The nomenclature for this mineral is not uniform. In the United States, the hydrated tubule form of the mineral is called endellite, and the dehydrated form is called halloysite. In Europe, the hydrated tubule form of the mineral is called halloysite, and the dehydrated form is called is called meta-halloysite. To avoid confusion, mineralogists will frequently refer to the hydrated mineral as halloysite 10 Å and the dehydrated mineral as halloysite 7 Å.
“Bates et al. present data on the tubes, which is summarized below:
Range (Å)Median (Å)Tube diameter:400-1900700Hole diameter:200-1000400Wall thickness:100-700 200
“Tube lengths range from 0.1 to about 0.75 μm. Morphologically, both hydrated and dehydrated halloysite comprise layers of single silica tetrahedral and alumina octahedral units. They differ in the presence or absence of a layer of water molecules between the silicate and alumina layers. The basal spacing of the dehydrated form is about 7.2 Å and the basal spacing of the hydrated form is about 10.1 Å. (hence the names halloysite 7 Å and halloysite 10 Å). The difference, about 2.9 Å, is about the thickness of a monolayer of water molecules.
“A theory for the formation of hollow tubular microcrystals is presented in Bates et al. Water molecules interposed between the gibbsite (Al2O3) and silicate (2SiO2) layers results in a mismatch between the layers, which is compensated by curvature of the layers.
“Halloysite 10 Å dehydrates to halloysite 7 Å at about 110° C. All structural water is lost at about 575° C. The interlayer water in halloysite 10 Å may be replaced by organic liquids such as ethylene glycol, di- and triethylene glycol, and glycerine.
“Another mineral that will, under appropriate hydration conditions, form tubules and other microstructures is imogolite.
“Another mineral that will, under appropriate conditions, form tubules and other microstructures is cylindrite. Cylindrite belongs to the class of minerals known as sulfosalts.
“Yet another mineral that will, under appropriate conditions, form tubules and other microstructures is boulangerite. Boulangerite also belongs to the class of minerals known as sulfosalts.”
In addition, the term “hydrated halloysite” is used in the claims of U.S. Pat. No. 4,019,934 of Takayama et al., the entire disclosure of which is hereby incorporated by reference into this specification. Claim 1 of this patent refers to an “inorganic gel.” Claim 4 of the patent recites that “4. The inorganic gel-ammonium nitrate composite material as claimed in claim 1 wherein said inorganic gel is prepared from a material selected from the group consisting of hydrated halloysite and montmorillonite.” As is disclosed in column 1 of such patent, “The purified and swollen inorganic gel prepared from a clay such as montmorillonite group, vermiculite, hydrated halloysite, etc., by the manner described hereinafter contains free water, bound water, and water of crystallization . . . . ”
In U.S. Pat. No. 5,651,976 of Price et al., there is disclosed and claimed in claim 1, “A composition for use in the delivery of an active agent at an effective rate for a selected time, comprising: hollow mineral microtubules selected from the group consisting of halloysite, cylindrite, boulangerite, and imogolite, wherein said microtubules have inner diameters ranging from about 200 Å to about 2000 Å, and have lengths ranging from about 0.1 μm to about 2.0 μm, wherein said active agent is selected from the group consisting of pesticides, antibiotics, antihelmetics, antifouling compounds, dyes, enzymes, peptides bacterial spores, fungi, hormones, and drugs and is contained within the lumen of said microtubules, and wherein outer and end surfaces of said microtubules are essentially free of said adsorbed active agent.”
In claim 11 of U.S. Pat. No. 5,651,976 of Price et al., there is disclosed and claimed, “A composition for use in the delivery of an active agent, at an effective rate for a selected time, into a fluid use environment wherein said active agent has a limited solubility, comprising: hollow cylindrical mineral microtubules selected from the group consisting of halloysite, cylindrite, boulangerite, and imogolite, wherein said microtubules have inner diameters ranging from about 200 Å to about 2000 Å, and have lengths ranging from about 0.1 μm to about 2.0 μm, wherein said active agent is selected from the group consisting of pesticides, antibiotics, antihelmetics, antifouling compounds, dyes, enzymes, peptides, bacterial spores, fungi, hormones, and drugs and is adsorbed onto an inner surface of said microtubules, wherein said microtubules are adherently coated with a coating, wherein said coating is wettable by said fluid and by said active agent, and wherein said coating is permeable to said active agent.”
Further information on the use of halloysite tubules for controlled delivery of active agents is disclosed in U.S. Pat. No. 5,705,191, “Sustained delivery of active compounds from tubules, with rational control,” of Price et al., the disclosure of which is incorporated herein by reference. In this patent, Price et al. disclose a method for releasing an active agent into a use environment, by disposing such active agent within the lumen of a population of tubules, and disposing such tubules into a use environment, either directly or in some matrix such as a paint in contact with the use environment. The tubules have a preselected release profile to provide a preselected release rate curve. The preselected release profile may be achieved by controlling the length or length distribution of the tubules, or by placing degradable endcaps over some or all of the tubules in the population, or by combinations of these methods. Price et al. further disclose a preferred population of tubules having a preselected release profile to provide a preselected release rate curve for controlled delivery of the active agent. In this patent, release rates are expressed in terms of Fick's second law for unsteady state diffusion, and in terms of certain tubule length distributions.
Yet another embodiment for a method involving the use of halloysite tubules is disclosed in U.S. Pat. No. 6,401,816, “Efficient method for subsurface treatments, including squeeze treatments” of Price et al., the disclosure of which is incorporated herein by reference. In this patent, Price et al. disclose a method for delivering encapsulated materials to a subsurface environment, for the treatment of such subsurface environment, having the steps of: (a) loading the lumen of hollow microtubules with an active agent selected for treating the subsurface environment, where the hollow microtubules are compatible with the subsurface environment; and (b) administering the hollow microtubules to the subsurface environment, permitting the controlled release of the active agent into the subsurface environment. The method may be practiced using a slurry of hollow microtubules, where the lumen of these microtubules is loaded with an agent for the treatment of petroleum well environments, and where these loaded microtubules are dispersed in a liquid phase carrier selected from aqueous carriers, non-aqueous carriers, and emulsions of aqueous and non-aqueous materials. The method may also be practiced using a pill made of a consolidated mass of tubules loaded with one or more active agents, typically bound with a binder. This method of Price et al is particularly related to treating subsurface liquid reservoirs, particularly oil reservoirs. More particularly, the method relates to treating oil reservoirs to prevent and/or remedy such problems as fouling of extraction wells by scale formation, well corrosion, and souring of oil by bacterial contamination, and to treating the liquid in such reservoirs by introducing chemical or biological agents, to affect the properties of the liquid or to aid in the extraction of the liquid.
U.S. Pat. No. 4,364,857, “Fibrous clay mixtures,” of Santilli discloses an application not involving the delivery of active agents from halloysite tubules, but rather the use of halloysite tubules in forming a catalyst support and a catalyst composition which have a large pore volume in 200-700 Angstroms diameter pores. With respect to a composition of matter, Santilli discloses, “codispersed rods of a first fibrous clay and a second fibrous clay, the first fibrous clay composed predominantly of fibers with a length range of 0.5-2 microns and a diameter range of 0.04-0.2 microns and a second fibrous clay predominantly composed of rods having a length range of 1-5 microns and a diameter range of 50-100 Angstroms. A preferred first clay is the tubular form of the clay halloysite and a preferred second clay is fibrous attapulgite. It is preferred that the composition be at least 5 percent attapulgite. It is preferred that the composition contain up to 15 percent of a binding refractory inorganic oxide. It is preferred that the refractory inorganic oxide be alumina. It is preferred that the catalyst body have a total pore volume of at least 0.35 cc/g and at least 60 percent of the volume of the pores is present in pores having diameters of 200-700 Angstroms. It is preferred that the composition also include at least one metal selected from the transition metals. This invention also comprises a method for hydroprocessing hydrocarbonaceous feedstocks comprising contacting the feedstocks with molecular hydrogen under hydroprocessing conditions in the presence of a catalyst having codispersed rods of a first fibrous clay having rods predominantly in the range of 0.5-2 microns with a diameter range of 0.04-0.2 microns and a second fibrous clay having rods in the range of 1-5 microns and a diameter range of 50-100 Angstroms. It is preferred that the first fibrous clay be halloysite and the second clay be attapulgite.”
With regard to the halloysite tubules, U.S. Pat. No. 4,364,857 of Santilli further discloses that, “The clay halloysite is readily available from natural deposits. It can also be synthesized, if desired. In its natural state, halloysite often comprises bundles of tubular rods or needles consolidated or bound together in weakly parallel orientation. These rods have a length range of about 0.5-2 microns and a diameter range of about 0.04-0.2 microns. Halloysite rods have a central co-axial hole approximately 100-300 Angstroms in diameter forming a scroll-like structure.
“It has been found that halloysite can make a suitable catalyst for use in demetalizing and hydroprocessing asphaltenes. The halloysite is processed to break up the bundles of rods so that each rod is freely movable with respect to the other rod. When substantially all the rods are freely movable with respect to all the other rods, the rods are defined herein as ‘dispersed’. When the dispersed rod clay is dried and calcined, the random orientation of the rods provides pores of an appropriate size for hydroprocessing and hydrodemetalizing asphaltene fractions.
“When halloysite rods or other rods of similar dimensions are agitated in a fluid such as water to disperse the rods, the dispersion can be shaped, dried and calcined to provide a porous body having a large pore volume present as 200-700 Angstroms diameter pores. When the shaping is by extrusion, however, it has been found that mixtures of dispersed clay rods of the halloysite type, do not extrude well. The rods on the surface of the extruded bodies tend to realign, destroying the desirable pore structure at the surface of the catalyst. This is defined herein as a ‘skin effect’. It has been discovered, however, that if a second fibrous clay with longer, narrower and presumably more flexible, fibers is codispersed with the halloysite-type clay, the resulting composition is easily extrudible, and there is no significant skin effect. ‘Codispersed’ is defined herein as having rod- or tube-like clay particles of at least two distinct types substantially randomly oriented to one another.”
It will be apparent from the disclosures of these United States patents of Price et al., and of Santilli, and from other known art pertaining to the controlled delivery of active agents from microtubules, that in many circumstances, it is desirable to provide and use a population of tubules for which the degree of purity and the tubule diameter and/or length distribution are known, and are preferably deterministically selectable. For the various active agents disclosed by Price et al. in the '976 patent, i.e., “pesticides, antibiotics, antihelmetics, antifouling compounds, dyes, enzymes, peptides, bacterial spores, fungi, hormones, and drugs,” it will be apparent that in processes and comprising such active agents, it will be necessary to deliver such active agents with a high degree of control. Accordingly, the degree of purity and the tubule diameter and/or length distribution for the halloysite tubules to be used may not be left to chance, i.e. “as delivered” directly from the mining operation.
Halloysite is mined and sold commercially from mines in New Zealand and in Juab County, Utah. Reference may be had to http://www.atlasmining.com/dragonmine.html, the web site of the Atlas Mining Company of Osborn, Id. which describes and shows certain operations of the Dragon Mine in the Tintic Mining District in Joab County, Utah. Although the halloysite clay obtained from the Dragon Mine is among the highest in purity and in proportion of microtubules, such halloysite clay is not obtained in a state that is suitable for direct use as a vehicle for loading and controlled release of active agents, or for use in other high precision applications such as e.g., ultracapacitors for use in electrical and electronics circuits and devices.
There has been an increased demand for portable energy storage devices in recent years due to the proliferation of portable electronics, cordless appliances, and a focus on renewable energy in applications such as hybrid gas/electric vehicles. Two common ways to store electrical energy in a portable package are batteries and capacitors. Unfortunately, standard capacitor technologies do not allow for sufficient energy storage for many of today's power applications.
In the 1950's and 1960's, it was observed that certain types of capacitors, specifically electrolytic capacitors, exhibit an electric double layer phenomenon. The storage of electric charge at the boundary of a metal and an electrolyte solution has been observed as far back as the nineteenth century. This charge storage phenomenon was later noted in electrolytic capacitor designs in the 1950's and 1960's. In 1969, Union Carbide Corporation filed a patent application, later issued as U.S. Pat. No. 3,581,159 entitled “Solid Electrolyte Capacitor Having Improved Counterelectrode System” that uses carbon particles to increase the capacitance of an electrolytic capacitor. The carbon particles exhibited an electric double layer phenomenon where additional charge was stored in and around the carbon particles that were added to the electrodes of an electrolytic capacitor. The Union Carbide patent attributed the increased capacitance in part to the increased surface area of the electrode due to the added carbon particles. U.S. Pat. No. 3,648,126, “Electrical Capacitor Employing Paste Electrodes,” discloses an electrolytic capacitor that uses a pair of paste electrodes made from active carbon and powdered metal to maximize the electrode/electrolyte surface area by providing a highly porous carbon electrode which forms extensive boundary surfaces on exposure to an electrolyte, thus forming a high surface area electrical double layer.
There have been recent attempts to increase the overall capacitance of an electrochemical capacitor by using techniques such as those disclosed in U.S. Pat. No. 6,704,192 entitled “Electrically Conductive, Freestanding Microporous Sheet For Use in an Ultracapacitor”. The '192 patent uses a microporous polymer sheet as an electrode in an electrochemical capacitor to create an electric double layer.
The growing demand for portable energy storage devices has created a renewed interest in new ways to create the electric double layer in capacitors that may increase the electrical charge storage potential of certain classes of electrochemical capacitors that are known as ultracapacitors or supercapacitors.
Accordingly, embodiments of the present invention are provided that meet at least one or more of the following objects of the present invention.
It is an object of the present invention to provide an electrode formed from mineral microtubules contained in a paste or a gel that can be used in an ultracapacitor.
It is a further object of the present invention to provide an electrode formed from mineral microtubules that are coated or embedded in a conductive polymer that can be used in an ultracapacitor.
It is yet another object of the present invention to provide a composite electrode formed from mineral microtubules that can be used in an ultracapacitor.
It is another object of the present invention to provide a hybrid electrode formed from mineral microtubules that can be used in an ultracapacitor.
It is still another object of the present invention to provide a hybrid composite electrode formed from mineral microtubules that can be used in an ultracapacitor.
It is a further object of the present invention to provide an ultracapacitor comprised of mineral microtubules wherein such ultracapacitor has high electrical capacitance.